riscv: efi: Generate Microsoft PE format compliant images

riscv: efi: Generate Microsoft PE format compliant images

Per Microsoft PE Format documentation [1], PointerToSymbolTable and
NumberOfSymbols should be zero for an image in the COFF file header.
Currently the COFF file header is hardcoded on RISC-V and these two
members are not zero.

This updates the hardcoded structure to clear these two members, as
well as setting the flag IMAGE_FILE_LOCAL_SYMS_STRIPPED so that we
can generate compliant *.efi images.

[1] https://docs.microsoft.com/zh-cn/windows/desktop/Debug/pe-format

Signed-off-by: Bin Meng <[email protected]>
Reviewed-by: Heinrich Schuchardt <[email protected]>
Signed-off-by: Alexander Graf <[email protected]>